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A New BFS "Smoking" Scheduler For Linux 3.3

03-25-2012, 09:20 AM

Phoronix: A New BFS "Smoking" Scheduler For Linux 3.3

Con Kolivas announced this weekend the release of an updated BFS scheduler for the recently-released Linux 3.3 kernel. The new BFS scheduler is at version 0.420 and is codenamed "Smoking", with "a fairly large architectural change" since earlier versions of this out-of-tree kernel scheduler...

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Why is it that some people go online, and write really lame-ass responses. "war". LOL. In my mail it said "fucking war". You removed the "fucking". Dude the whole thing is really lame. Forget about "war". Forget about "more responsive". 0.33ms = feels like vintage hardware. And they are always working to push that down, because os-jitter = worse performance with several cpu`s, and that means low latency = good.

If you ask me, Con seems to be wasting his time. If he is complaining it is taking too much of his time, he should just forget about it. Unless he has some personal quest for his dual core. Generally it is not a noticable gain for most, and I think that was who he had in mind, in the beginning.

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I think those benchmarks really give a good indication of the current state of CFS vs BFS.

CFS is actually more fair now, at the cost of worst case latency. It does have higher overall throughput.

BFS is somewhat unfair (but still generally within a percent or two of being completely fair) and yet has much lower latency in some test (as much as 100% less latency). But the cost of achieving that low latency is hurting throughput and overall maximum number of threads.

So, use what's best for your workload. I'd say CFS has made many improvements, and is really a generally good scheduler.

Where as BFS is still the best scheduler if all you care about is low latency.

EDIT: I also just read an attached academic paper, and it confirms that BFS does give very good fairness in worse case type scenarios that aren't predictable. BFS does well in workloads where the caches can't be guaranteed to work, e.g. cache misses (sounds like Desktop workloads to me). Where as CFS does well in predictable throughput based benchmarks, and it scales to lots of cores. BFS theoretically wouldn't scale too far since it has a global runqueue.

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He has a quad core, not dual. And the improvements can be felt but also measured. You can find plenty of results and graphs.

So no. He is not wasting his time. For a lot of people, Linux wouldn't be the same without CK's work.

Btw, writing "peace" at the bottom of your posts does not make you look cool. Unless you're Jamaican. Otherwise you're just a poser.

Oh man. You did not understand about 0.33ms latency, and claim you can "feel" the difference. When the task is ready it is diplayed on screen. If the latency is 0.33ms, max time for short tasks = 0.33ms, and it is displayed the next frame. You cannot feel the difference here.

So YES it is a waste of time. The only gains now are for multiple CPU`s. And that is not what his work is about.

And your repulsive ignorance with "peace" etc, is inexpressibly stupid. Get educated, learn about some other cultures. And you will find it is a common greeting, and in groups far larger than jamaicans, rastafari, and hasish smoking.

I actually tried mainstream kernel, on doom3, with 0.33 ms. It plays like it should have been written in asm for custom hardware arcades. It doesn`t get more responsive than that. If he has a problem, then it is not with the kernel.